Process for the production of compression ignition engine, gas turbine, and fuel cell fuel and compression ignition engine, gas turbine, and fuel cell fuel by said process

ABSTRACT

The invention provides a Fischer-Tropsch derived compression ignition engine, gas turbine, and fuel cell fuel which is interchangeably useable in compression ignition engines, gas turbines, and fuel cells, said fuel selected from a substantially C5 to C9 cut, a substantially C5 to C9 cut blended with a substantially C9 to C14 cut, a substantially C5 to C9 cut blended with a substantially C9 to C14 cut and a substantially C14 to C22 cut, and a substantially C5 to C9 cut blended with a substantially C14 to C22 cut. The invention extends to a process for preparing said fuel and the use of such a fuel in a CI engine, and HCCI engine, a turbine, and/or a fuel cell.

CROSS RELATED APPLICATION(S)

This application is a continuation of PCT Patent ApplicationPCT/ZA2004/000125 filed Oct. 14, 2004 and published on Apr. 4, 2005 asWO 2005/035695, which claims priority to ZA 2003/8080 filed Oct. 17,2003 and U.S. Provisional Application 60/512,330 filed Oct. 17, 2003.

FIELD OF THE INVENTION

The invention relates to the production of compression ignition engine,gas turbine, and fuel cell fuels.

BACKGROUND TO THE INVENTION

In this specification, the term “multipurpose hydrocarbonaceous energysources” is abbreviated to MES and is used in both the singular and theplural.

The term MES thus encompasses compression ignition engine, gas turbine,and fuel cell fuels.

An MES usable in gas turbines, compression ignition (CI) engines,including Homogeneous Charge Compression Ignition (HCCI) systems or fuelcells is an attractive option for many energy users, especially forthose operating in remote stranded locations where a single form ofsupply of energy is required and simplified logistics are necessary.These entities include users in many classes of human activity.

U.S. Pat. No. 6,475,375, discloses the process for the production of asynthetic naphtha fuel usable in CI engines. This patent, however, doesnot contemplate the use of such a fuel as an MES having broaderapplication other than use thereof in a CI engine. Thus, the disclosurein this patent does not provide any indication of how the problemsassociated with the production of an MES may be overcome or whatcharacteristics or properties such an MES should have.

A synthetic multi-purpose fuel useful as a fuel cell fuel, diesel enginefuel, gas turbine engine fuel and furnace or boiler fuel are disclosedin PCT WO 01/59034. The multi-purpose fuel produced ranged from C9 toC22.

The inventor has now identified a need and a process for at leastpartially satisfying such an MES need.

The Fischer-Tropsch (FT) process is a well known process in which carbonmonoxide and hydrogen are reacted over an iron, cobalt, nickel orruthenium containing catalyst to produce a mixture of straight andbranched chain hydrocarbons ranging from methane to waxes with molecularmasses above 1400 and smaller amounts of oxygenates. The feed for the FTprocess may be derived from coal, natural gas, biomass or heavy oilstreams. The term Gas-to-Liquid (GTL) process refers to schemes based onnatural gas, which is mainly methane, to obtain the synthesis gas, andits subsequent conversion using in most instances an FT process. Thequality of the GTL FT synthetic products is essentially the sameobtainable from the FT process here defined once the synthesisconditions and the product work-up are defined.

The complete process can include gas reforming which converts naturalgas to synthesis gas (H₂ and CO) using well-established reformingtechnology. Alternatively, synthesis gas can also be produced bygasification of coal or suitable hydrocarbonaceous feedstocks likepetroleum based heavy fuel oils. The synthesis gas is then convertedinto synthetic hydrocarbons. The process can be effected using, amongothers, a fixed-bed tubular reactor or a three-phase slurry reactor. FTproducts include waxy hydrocarbons, light liquid hydrocarbons, a smallamount of unconverted synthesis gas and a water-rich stream. The waxyhydrocarbon stream and, almost always, the light liquid hydrocarbons arethen upgraded in the third step to synthetic fuels such as diesel,kerosene and naphtha. Heavy species are hydrocracked and olefins andoxygenates are hydrogenated to form a final product that is highlyparaffinic. Hydrocracking and hydrogenation processes belong to thegroup sometimes generally named hydroconversion processes.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided amultipurpose carbonaceous energy source (MES fuel) which is acompression ignition engine, gas turbine, and fuel cell fuel which fuelis interchangeably useable in compression ignition engines, gasturbines, and fuel cells, said energy source selected from:

-   -   a substantially C5 to C9 cut blended with a substantially C9 to        C14 cut, said blend having an H:C molar ratio from 2.18 to 2.24;    -   a substantially C5 to C9 cut blended with a substantially C9 to        C14 cut and a substantially C14 to C22 cut, said blend having an        H:C ratio from 2.12 to 2.18; and    -   a substantially C5 to C9 cut blended with a substantially C14 to        C22 cut, said blend having an H:C molar ratio from 2.13 to 2.19.

The MES fuel options as defined in this invention are summarised inTable 1. TABLE 1 MES Fuels Carbon Number Range H:C CO₂ Fuel Cut A Cut BCut C Ratio Emissions MES Cut C5-C9 C9-C14 C14-C22 Molar g CO₂/g fuel 1C5-C9 X 2.29 3.080 2 C5-C14 X X 2.20 3.098 3 C5-C22 X X X 2.14 3.111 4C5-C9 & X X 2.17 3.105 C14-C22

The MES fuel may, when combusted, have a CO₂ emission below 3.115 gCO₂/g fuel combusted.

One or more of the C5 to C9, C9 to C14, and C14 to C22 cuts may besynthetic in origin.

One or more of the C5 to C9, C9 to C14, and C14 to C22 cuts may beFischer-Tropsch process in origin.

The MES Fuel may be a partially or totally synthetic fuel.

The MES Fuel may be a Fischer-Tropsch process derived fuel.

According to a second aspect of the invention, there is provided aprocess for the production of synthetic multipurpose carbonaceous energysource (MES fuels) which is a compression ignition engine, gas turbine,and fuel cell fuel, which fuel is interchangeably useable in compressionignition engines, gas turbines, and fuel cells, said process includingthe steps of:

-   a) oxidising a carbonaceous material to form a synthesis gas;-   b) reacting said synthesis gas under Fischer-Tropsch reaction    conditions to form Fischer-Tropsch reaction products;-   c) fractionating the Fischer-Tropsch reaction products to form one    or more MES blending components selected from the group including:    -   A. a C5 to C9 cut;    -   B. a C9 to C14 cut; and    -   C. a C14 to C22 cut; and-   d) using said blending components in the production of the MES,    provided that where at least one of the blending components is a    blending component in the C9 to C14 or in the C14 to C22 boiling    range then at least two blending components are used in the    production of the MES, one of which is the C5 to C9 cut.

The C5 to C9 cut may be a light hydrocarbon blend, typically in the35-160° C. distillation range.

The C9 to C14 cut may be a medium hydrocarbon blend, typically in the155-250° C. distillation range.

The C14 to C22 cut may be a heavy hydrocarbon blend, typically in the245-360° C. distillation range.

To obtain the MES fuels of Table 1, the blending components A, B and C,as described above, may be blended in a volumetric ratio of A:B:C of:

1.0:0.0:0.0 for MES 1

and

1.2:1.0:0.0 for MES 2

1.8:1.0:2.3 for MES 3

1.0:0.0:2.1 for MES 4

to

1.0:1.2:0.0 for MES 2

1.0:1.2:1.8 for MES 3

1.0:0.0:1.5 for MES 4

To obtain the MES fuels of Table 1, the blending components A, B and Cmay be blended in a volumetric ratio of A:B:C, wherein:

A may be from 1 to 2;

B may be from 0 to 1.5; and

C may be from 0 to 2.5.

One or more of the blending components may be hydroconverted.

Thus, the MES may be a blend of both hydroconverted and unhydroconvertedblending components.

The MES may be a product of one or more of only unhydroconvertedblending components.

The MES may be a product of one or more only hydroconverted blendingcomponents.

The Fischer-Tropsch process of step b) may be the Sasol Slurry PhaseDistillate™ process.

The carbonaceous material of step a) may be a natural gas stream, anatural gas derivatives stream, a petroleum gas stream, a petroleum gasderivatives stream, a coal stream, a waste hydrocarbons stream, abiomass stream, and in general any carbonaceous material stream.

Optionally, hydrogen may be separated from the synthesis gas eitherduring or after step a).

This hydrogen may be used in the hydroconversion of FT primary products,namely FT condensate and FT wax.

Table 2 below gives a typical composition of the FT condensate and FTwax fractions. TABLE 2 Typical Fischer-Tropsch product after separationinto two fractions (vol % distilled) FT Condensate FT Wax (<270° C.fraction) (>270° C. fraction) C₅-160° C. 44 3 160-270° C. 43 4 270-370°C. 13 25 370-500° C. 40 >500° C. 28

In one embodiment of the invention, the hydroconverted products arefractionated in a common distillation unit where at least three blendingcomponents are recovered:

-   (1) a light hydrocarbon blend, typically in the 35-160° C. ASTM D86    distillation range, i.e. C5 to C9;-   (2) a medium hydrocarbon blend, typically in the 155-250° C. ASTM    D86 distillation range, i.e. C9 to C14; and-   (3) a heavy hydrocarbon blend, typically in the 245-360° C. ASTM D86    distillation range, i.e. C14 to C22.

However, in other embodiments, the FT condensate and FT wax are blendedtogether before being fractionated into the blending components.

In some embodiments the FT condensate is transferred directly to theproducts fractionator without any hydroconversion stage.

When processing using this approach, the MES products benefit from thesynergy of the composition and quality of the wax and condensatefractions.

MES fuels of the invention meet the fuel requirements of many classes ofenergy conversion systems including gas turbines, CI engines, includingHCCI systems and fuel cells.

The MES compositions may have the following properties which make itsuitable for fuel cells, gas turbine engine and CI engines (as shown inTable 3 below): TABLE 3 Quality of the Multipurpose Energy Sources LightHC Medium Heavy HC Blend HC Blend Blend MES-1 MES-2 MES-3 Yield (est.)wt % 28% 25% 47% 28% 53% 100% Density @ 15° C. kg/l 0.690 0.752 0.7820.690 0.723 0.747 Cetane Number (IQT) 44 64 >72 44 60 64 Sulphur wt ppm<1 <1 <1 <1 <1 <1 ASTM D86 Distillation range ° C.  35-160 155-250245-360  35-160  35-250  35-360 Cold Filter Plugging Point ° C. <−30<−30 −12 <−30 <−30 <−30 Freezing point ° C. <−60 −48 −9 <−60 <−60 <−60Flash Point ° C. <0 50 114 <0 <0 14 Aromatics wt % 1.0-2.0 0.5-1.0 <0.51.0-2.0 1.0-1.5 0.5-1.0 Biodegradabily Test pass pass pass pass passpass Thermal stability Visual rating 1 (Excellent) 1 (Excellent) 1(Excellent) 1 (Excellent) 1 (Excellent) 1 (Excellent) (Octel F21-61)(relative stability) Oxidation Stability mg/100 ml 0.1 0.1 0.2 0.1 0.10.1 Viscosity @ 40° C. cSt 0.98 1.14 3.3 0.98 1.10 1.34HC = Hydrocarbon

High Cetane Number: Fuels with a high cetane number ignite quicker andhence exhibit a milder uncontrolled combustion because the quantity offuel involved is less. A reduction of the uncontrolled combustionimplies an extension of the controlled combustion, which results inbetter air/fuel mixing and more complete combustion with lower NOxemissions and better cold start ability. The shorter ignition delayimplies lower rates of pressure rise and lower peak temperatures andless mechanical stress.

The cetane number of the MES compositions was determined according toASTM D613 test method and an Ignition Quality Tester (IQT—ASTM D6890).

Near Zero-Sulphur Content: The sulphur content was determined accordingto the ASTM D5453 test method. The less than 1 ppm sulphur present inthe MES compositions not only make the components suitable for a fuelcell reformer catalyst, but also contribute to the lower exhaustemission in engines, such as CI engines. The less than 1 ppm sulphurpresent in the MES composition either ensure compatible with certainexhaust catalyst devises or give improved compatibility with other.

Good Cold Flow Properties: Cold Filter Plugging Point (CFPP) is thelowest temperature at which the fuel can pass through a standard testfilter under standard conditions (requires more than 1 minute for 20 mlto pass through a 45-μm filter). This test is done accordingly to theInstitute of Petroleum IP 309 method or equivalent. Inadequate cold flowperformance will lead to difficulties with starting and blockage of CIengine fuel filters under cold weather conditions.

Freezing point is one of the physical properties used to quantitativelycharacterise gas turbine engine fuel fluidity. The low freezing point,determined in accordance with the automated ASTM 5901 test method, orequivalent, can be attributed to the more than 60 mass % iso-paraffinspresent in MES compositions.

Excellent Thermal and Oxidation Stability: The thermal stability of theMES compositions was determined according to the Octel F21-61 testmethod where a visual rating was used to describe the relativestability. The FT products lead to significantly less carbon depositionon the fuel cell reformer catalyst than would be expected from aconventional diesel type feedstock under comparative reactionconditions.

Oxygen stability is tested through the calculation of the amount ofinsolubles formed in the presence of oxygen. It measures the fuel'sresistance to degradation by oxygen by the ASTM D2274 test method orequivalent. The MES compositions are stable in the presence of oxygenwith the formation of insolubles of less than 0.2 mg/100 ml.

High Hydrogen To Carbon Content: The highly paraffinic nature of the FTproducts and very low aromatic concentration contribute to the high H:Cratios of the MES compositions.

In Table 1, four illustrative MES formulations are shown which have beenfound compatible with their proposed use in gas turbines, CI engines,including HCCI systems and fuel cells. The expected quality andestimated yields of the MES formulations of Table 1 are presented inTable 3.

The MES compositions may be suitable for use in fuel cells, gas turbineengine and Cl engines, including HCCI systems as they contain FTreaction derived products which are highly saturated with less than 2volume % olefins, have ultra-low levels of sulphur with an almost zeroaromatic hydrocarbon content, high linearity, high hydrogen to carbonratio, very good cold flow properties, and high cetane number.

Lower reformer temperatures in fuel cells are required with the use ofFT naphtha, kerosene or diesel. The FT products lead to significantlyless carbon deposition on the catalyst than would be expected from aconventional diesel type feedstock under comparative reaction conditionsand produce more steam. The MES components have good cold flowproperties as well as a high cetane number because of the predominantlymono-, and to a lesser extent other, branched forms of the paraffinswhich make these components suitable for application in gas turbineengines, Cl engines, including HCCI systems and fuel cells.

The highly paraffinic related properties such as high H:C ratio, highcetane number and low density together with virtually zero-sulphur andvery low aromatics content give the FT products their very good emissionperformance

DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of non-limiting example onlywith reference to the accompanying drawings. In the drawings,

FIG. 1 shows a flow sheet for a process for the production of a fuel ofthe invention;

FIG. 2 shows a flow sheet for an alternative process to that in FIG. 1but based on Natural gas;

FIG. 3 shows a flow sheet for a process using high molecular massfeedstocks; and

FIG. 4 shows a flow sheet for a process such as that of FIG. 3 using useof coal, biomass or heavy oil as feedstock.

PROCESS DESCRIPTION

This invention includes four possible processes for the production ofMES components i.e. components for Fischer-Tropsch derived compressionignition engine, gas turbine, and fuel cell fuel which isinterchangeably useable in compression ignition engines, gas turbines,and fuel cells. Two of them are based in the use of natural gas as feedand, the other two make use of any hydrocarbonaceous feedstock possibleof been gasified. Therefore, feeds for the latter include coal, waste,biomass and heavy oil streams.

The first process matter of this invention, presented in FIG. 1, makesuse of natural gas 11 which is converted to synthesis gas at suitableprocess conditions in reformer 1. The reforming reaction makes use ofoxygen 13 obtained from an air separation step 2 from atmospheric air12. Water in the form of steam can also be used in the reformingprocess.

Syngas 14 from the reformer stage is converted in FT unit 3 to synthetichydrocarbons including at least two liquid streams, as well as a gasstream and reaction water not shown. A portion of the syngas might bederived from the hydrogen separation plant 4 where a hydrogen richstream 17 is produced for use in hydroconversion. Alternatively,hydrogen can be produced in an independent facility and transferred asstream 17.

The light synthetic hydrocarbons stream 15, sometimes named FTCondensate, includes paraffins, olefins and some oxygenates, mostlyalcohols. This stream is transferred to hydrotreating unit 6 whereolefins and oxygenates are hydrogenated into, mostly, the correspondingparaffin hydrocarbons. The process is completed at conditions such thatthe average carbon number of the feed remains essentially unchanged inhydrotreated product 18.

The heavy synthetic hydrocarbons 16, sometimes named FT Wax, has asimilar chemical composition as that of the lighter stream 15; however,under normal processing these species are solid at room temperature.This stream is transferred to the hydroconversion unit 5, preferably ahydrocracker system, where (1) olefins and oxygenates are hydrogenatedto the corresponding paraffins which in turn and together with theoriginal long chain paraffins (2) undergo cracking reactions resultingin a significant reduction of its average carbon number compared withthat of the feed. The resulting hydrocracked product 19 is a mixture ofnormal and iso-paraffins.

The combined hydroconverted products 18 and 19 are fractionated indistillation unit 7 resulting in at least four process streams. Stream20 is a light hydrocarbon blend, typically in the 35-160° C. ASTM D86distillation range. Stream 21 is a medium hydrocarbon blend, typicallyin the 155-250° C. ASTM D86 distillation range. Stream 22 is a heavyhydrocarbon blend, typically in the 245-360° C. ASTM D86 distillationrange. Stream 23 includes unconverted species whose boiling points areabove 360° C. and is recycled to the hydrocracker to increase theproduction of the valuable species. The separation process also resultsin collecting a gas stream—not shown.

The MES products are produced using these streams on their own or inblends as shown in Table 1 above.

An alternative second process scheme based on natural gas is presentedin FIG. 2. From a process standpoint it differs from the one describedbefore in that the light synthetic hydrocarbons 15 is not hydrotreated.Instead it is blended with the hydrocracked product 18. The resultingstream 19 is fractionated then in distillation unit 7 resulting inproducts 20-22 similar to those above described. However, while theseproducts can be used in the same blends, they include some olefins andoxygenates in their composition.

Using alternative high molecular mass feedstocks this invention providesthe process scheme shown in FIG. 3. This concept makes use of coal,biomass or heavy oil which in the form of stream 11 is converted tosynthesis gas at suitable process conditions in gasifier 1. Thegasification process makes use of oxygen 13 obtained from an airseparation step 2 from atmospheric air 12. Water in the form of steamcan also be used in the process. This process is then substantiallysimilar to the one discussed before with reference to FIG. 1. However,and as an additional stream, some liquids are produced during thegasification process and separated as stream 24. These might berecovered as a product or recycled to the gasifier to enhance productionof the valuable streams. Other than this, process units and streams inFIG. 3 correspond to those in FIG. 1 and its associated processdescription

Finally, and as an alternative to this concept, it is provided a fourthprocess scheme similar in essence to the second option discussed hereabove. As the one just discussed, this makes use of coal, biomass orheavy oil as feedstock and makes use of gasifier 1 as described in theprevious paragraph. This process is then substantially similar to theone discussed before with reference to FIG. 2. However, and as anadditional stream, some liquids are produced during the gasificationprocess and separated as stream 24. These might be recovered as aproduct or recycled to the gasifier to enhance production of thevaluable streams. Other than this, process units and streams in FIG. 4correspond to those in FIG. 2 and its associated process description.

1-12. (canceled)
 13. A compression ignition engine, gas turbine, andfuel cell fuel which is interchangeably useable in compression ignitionengines, gas turbines, and fuel cells, said fuel comprising asubstantially C5 to C9 hydroconverted cut blended with a substantiallyC9 to C14 hydroconverted cut, which cuts have the Fischer-Tropschprocess as their origin, said blend having, an H:C molar ratio from 2.18to 2.24.
 14. A compression ignition engine, gas turbine, and fuel cellfuel which is interchangeably useable in compression ignition engines,gas turbines, and fuel cells, said fuel comprising a substantially C5 toC9 hydroconverted cut blended with a substantially C9 to C14hydroconverted cut and a substantially C14 to C22 hydroconverted cut,which cuts have the Fischer-Tropsch process as their origins said blendhaving an H:C ratio from 2.12 to 2.18.
 15. A compression ignitionengine, gas turbine, and fuel cell fuel which is interchangeably useablein compression ignition engines, gas turbines, and fuel cells, said fuelcomprising a substantially C5 to C9 hydroconverted cut blended with asubstantially C14 to C22 hydroconverted cut, which cuts have theFischer-Tropsch process as their origin, said blend having an H:C molarratio from 2.13 to 2.19.
 16. A compression ignition engine, gas turbine,and fuel cell fuel as claimed in claim 13, having an oxidation stabilityof equal or less than 0.2 mg/100 ml.
 17. A compression ignition engine,gas turbine, and fuel cell fuel as claimed in claim 14, having anoxidation stability of equal or less than 0.2 mg/100 ml.
 18. Acompression ignition engine, gas turbine, and fuel cell fuel as claimedin claim 15, having an oxidation stability of equal or less than 0.2mg/100 ml. 19-21. (canceled)